Expansion bands are well known in the prior art and are typically constructed of interconnected outer and inner overlapping links. Each outer link is connected to a pair of inner links by means of U-shaped connecting members commonly referred to as "staples". The links are generally shaped as elongated hollow boxes with openings at either end to receive the legs of the staples. The staples are retained in engagement with the inner and outer links by folded end tabs or other means. Groups of links are connected in an adjacent line to form a band of an appropriate length. A force tending to stretch the band will pivot the staples within each link to separate the links and provide an expansion capability of around 3 to 5 inches. Springs provided in the links yieldingly resist the pivoting motion of the staples, thereby biasing the band into a contracted state. In the contracted state the outer links meet so that adjacent sides of successive links are touching to provide a pleasing decorative outer finish to the band. In this state, the staples extend generally perpendicular to a reference plane extending between the overlapping inner and outer links. FIG. 1 is illustrative of this prior art construction.
The following patents all show variations of this construction and are also typical of the prior art:
U.S. Pat. Nos. 2,689,450; 3,158,989; 2,918,785; 3,307,347; 2,799,135; 3,307,348; 2,941,351; 3,315,463; 2,957,303; 3,543,507; 3,786,629.
The decorative appearances of the prior art bands is provided either by the outer faces of the outer links, or more preferably by top shells applied as decorative covers to the outer links. Until now, the variety of styles available through the use of decorative top shells has been significantly limited by functional considerations relating to band expandability. More particularly, those skilled in the art are well aware of the necessity to provide a spacing between the inner links of a contacted band in order to avoid pinching the skin and hair on a wearer's wrist. However, such spacing must be kept to a minimum, for otherwise the expandability of the band will be unacceptably compromised.
In the prior art bands, the inner and outer links either have substantially equal width dimensions (U.S. Pat. No. 2,799,135), or the outer links are wider than the inner links (U.S. Pat. No. 3,786,629). In both cases, the extent to which the top shells can protrude laterally beyond the widths of the outer links is severely limited because any such protrusions further increase the spacing between the inner links, with a concomitant decrease in expandability. Thus, the top shells must either substantially conform in design as well as in size to the underlying outer links (FIG. 1 of U.S. Pat. No. 2,799,135 and FIG. 13 of U.S. Pat. No. 3,786,629), or the outer links must themselves be specially contoured to accommodate the design of the top shells (FIGS. 14-17 of U.S. Pat. No. 3,786,629).
The first alternative stifles design freedom, and the second alternative is equally unacceptable in that it requires specially designed outer links to be provided for each top shell variation.
A primary objective of the present invention is to provide an expansion band wherein the inner and outer links are dimensionally related in a manner such as to accommodate significantly greater lateral protrusions of the top shells beyond the widths of the outer links.
A companion objective of the present invention is to provide an expansion band which allows a wide variety of decorative shells to be applied to the outer links without unduly restricting the expansion capability of the band, and without requiring specially contoured outer links for each top shell design.